Pneumatic-electric switch



May 4, 1965 L. s. SMITH PNEUMATIC-ELECTRIC SWITCH 3 Sheets-Sheet 1 Filed May 25, 1962 INVENTOR Lorry S. Smith JdI ATTORNEY May 4, 1965 3 Sheets-Sheet 2 Filed May 25, 1962 INVENTOR Larry S. Smith v n 3 n vm 2 mm I 2 mm OT. 3 No v Q. I. wm vv mw an 9 mm we r oo. 2: 8 om ATTORNEY y 1965 5. SMITH 3,182,150

PNEUMATIC-ELECTRIC SWITCH Filed May 25, 1962 3 Sheets-Sheet 3 FIG.5.

FIG.6.

- Manon Lorry S. Smith ATTORNEY United States Patent 3,182,150 PNEUMATIC-ELECTRIC SWITCH Larry Secor Smith, Goshen, Ind., assignor to Robertshaw Controis Company, a corporation of Delaware Filed May 25, 1962, Ser. No. 197,730 7 Claims. (Cl. 200-433) This invention relates to pneumatic-electric switch means and more particularly, to a differential lever and biasing means therefor for connecting the actuating source of pneumatic pressure to the electric switch means.

It is an object of this invention to provide a pneumaticelectric switch operated from one state to another in response to a positive change in signal pressure.

Another object of this invention is to provide a pneumatic-electric switch, operated from one state to another in response to a positive change in signal pressure, having a novel and readily adjustable differential actuating lever means.

Still another object of this invention is to provide a pneumatic-electric switch, operated from one state to another in response to a positive change in signal pressure, having a novel and readily adjustable differential actuating lever means, wherein said lever means includes first and second interacting levers, one having an adjustable range setting means acting thereon and the other having an adjustable pressure differential setting means acting thereon.

These and other objects of the present invention will become apparent with reference to the following specification and drawings which relate to a preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a top plan view of the invention;

FIGURE 2 is a side elevation of the invention in partial cross-section taken along line 2-2 of FIGURE 1;

FIGURE 3 is a perspective of the invention completely enclosed in a casing;

FIGURE 4 is a schematic representation of a switch used with the present invention;

FIGURE 5 is an enlarged top elevation of a detail of the invention; and

, FIGURE 6 is a :side elevation with a partial cross-section taken along line 6-6 of the detail of FIGURE 5.

Referring in detail to the drawings, and more particularly to FIGURES 1 and 2, the pneumatic-electric switch of the present invention is shown as including an electric switch unit 10 mounted between two pairs of upstanding ears 12 and 14 on a bracket 16 which, in turn, is supported by base 18 in a housing 20.

A pressure connection 22 is provided in the lower wall 24 of the housing 24) and extends to an external source of signal pressure (not shown). Internally of the casing adjacent the pressure connection 22, and clamped between the lower wall 24 thereof and the base 18, is a flexible diaphragm 26 forming an expansible pressure signal chamber 28 in communication with the inlet port 3% from the said pressure connection 22.

The base 18 has the lower side thereof hollowed out to form a second chamber 32 of substantially the same size as the pressure signal chamber 28 directly opposite the said signal chamber on the other side of the diaphragm 26. This permits freedom of movement of the diaphragm 26 in response to pressure signals received in the signal chamber 28.

The diaphragm 26 carries a centrally positioned diaphragm button 34 and upstanding transmitting link 36, which link extends upward through an opening 38 in the base 18, whereby motion of the diaphragm 26 may be transmitted to a differential switch actuating lever means to be hereinafter described.

The bracket 16 holding the switch unit It} is positioned Patented May 4, 1965 above the surface of the base 18 by means of a bent tang 40 and a pair of hold-down screws 42 on one end and a leveling screw 44 threaded through a straight tang 46 on the other end thereof. Both the outer end of the bent tang 49 and the lower tip of the leveling screw 4-4 abut the lands of upstanding integral studs 48 and 5%, respectively, on the base 18.

Referring additionally to FIGURES 5 and 6, the differential actuating lever means is shown as comprising a first or actuating lever 52 and a second or differential lever 54.

As shown, the actuating lever 52 is mounted beneath the diiferential lever 54-, both levers being mounted on a common pivot rod 56 extending between a pair of downwardly extending ears 58 (FIGURE 6) located one on either side of the switch unit mounting bracket 16.

As best shown in FIGURES 5 and 6, the actuating lever 52 is channel-shaped and open at the top and is pivoted intermediate the ends thereof by means of upstanding ears 60 (FIGURE 6) which receive the pivot pin 56 internally of the ears 58. The differential lever 54 is shown as comprising an inverted channel-shaped member of sufficient size to internally receive the actuating lever 52.

As shown in FIGURES 2 and 6, the actuating lever 52 extends from an integral switch engaging detent 62 on one side of the pivot 56 to an integral downwardly opening upstanding hollow stud 64 therein on the other side of the pivot 56 for receivably engaging the transmit ting link 36 from the flexible diaphragm 26. An opening 66 in the web of the actuating lever 52 is provided to permit the leveling screw 44 on the switch bracket 16 and the upstanding stud 59 on the base 18 to protrude therethrough without affecting the operation of the said actuating lever.

Still referring to FIGURES 2 and 6 along with FIG- URES 1 and 5, the differential lever 54 is shown as being bifurcated at one end by removing the Web from between the channel side portions 68. The outer ends of the channel side portions 66 receivably engage the pivot pin 56 externally of the ears 60 on the bracket 16. A spring lock or E-ring 70 is provided on both ends of the pivot pin 56 to maintain the pivotal assembly. At the root of the bifurcated end portion, a portion of the channel web is bent downward at right angles between the channel sides 68 to form an integral tongue or limit stop 72 on the differential lever 54. As best shown in FIGURES 2 and 6, the limit stop 72 on the differential lever 54 is adapted to engage the web portion of the actuating lever 52 whereby a predetermined minimum spacing between the said levers is effected.

Immediately behind the limit stop 72 in the Web of the differential lever 54 and directly adjacent the hollow stud 64 in the actuating lever 52, is an opening 74 providing access to the stud 64 in the actuating lever 52 through the differential lever 54 for a purpose to be hereinafter described. From the opening 74, the differential lever 54 extends past the end of the actuating lever 52 and terminates in an integral downwardly opening upstanding hollow stud 76.

The hollow stud '76 receivably engages, as shown in FIGURE 2, an upstanding limit stop screw '78 in the base 18 which provides a predetermined. minimum spacing between said differential lever 54 and the base 18.

Referring now to FIGURES l and 2 an open ended arch or hood 8%) is shown as being substantially coextensive with the pressure inlet and diaphragm confining portion of the base 18. The hood, for example, may comprise upstanding integral side portions 62 on the base 18 (FIGURE 2) topped by a cap-plate 84 held in place by four hold-down screws 86 (FIGURE 1).

The underside of the cap-plate 84 includes a pair of counterbores 88 and 9% each forming a downwardly facing internal shoulder 92 and 94-, respectively. These shoulders 92 and 94 are respectively positioned directly above the hollow studs 64 and 76 on the actuating lever 52 and differential lever 54, respectively.

Both of the studs 64 and 76 provide short upwardly extending cylinders which are, respectively, internally received in the bottom ends of a range spring 96 and a differential spring 95, the said springs respectively resting on the Web portions of the actuating lever 52 and the differential lever 54- peripherally adjacent the said studs.

The upper ends of the range and differential springs 96 and 95 are selectively confined by a pair of conformally shaped end plates 1% and 1112, respectively, each of the said end plates having, respectively, an internally threaded bore 104- and 1%. t

A range adjusting screw 108 is threadably received in the bore 1% of the end plate and extends therethrough internally coaxial with the range spring 96. The

head of the range screw 108 is slotted in a conventional manner at 110 and includes an enlarged integral concentric flange portion 112 which abuts the downwardly facing internal shoulder 92 in the counterbore 91), whereby the range spring 96 is adjustably confined between the cap-plate 84 and the stud 64 on the actuating lever 52 by its own compressive force. The head of the range screw 168 is sufficiently elongated so that the slotted portion 110 thereof extends through the bore 88 to a point above the top of the cap-plate S4.

A dilferential adjusting screw 114 is threadably received in the bore 1% of the end plate 162 and extends therethrough internally coaxial with the differential spring 98. The head of the differential screw 114 is slotted in a conventional manner at 116 and includes an enlarged integral concentric flange portion 118 which abuts the downwardly facing internal shoulder $4 in the counterbore 5 0, whereby the diiferential spring 93 is adjustably confined between the cap plate 84 and the stud 76 on the differential lever 54 by its own compressive force. The head of the differential screw 114 is sufliciently elongated so that the slotted portion 116 thereof extends through the bore 91 to. a point above the top of the cap-plate 84.

Referring now to FIGURE 4, the electric switch unit .10 controlled by the differential lever means is shown 1 as comprising normally open contact 120 with an external terminal screw 122, a normally closed contact 124 with an external terminal screw 126 and a common contact 128 having an external terminal screw 13%.

The common contact 128 is mounted onthe free end of a cantilever type contact spring 132 having a down- 7 wardly extending integral operating push-link 134 thereon which extends through an opening in the switch housing and mounting bracket 16 into engagement with the switch engaging detent 62 on the actuating lever 52.

To complete the entire assembly of the invention for purposes of installation, referring now to FIGURES 1, 2 and 3, the base plate 2 1 of the casing 20 is shown to actually comprise an integral part of a channel-shaped casing open on three sides; at the top and both ends of the insulating base 18. 7

As shown in FIGURE 3, a cover portion 136 of a conforming channel-shape is provided to close the three open sides of the casing 20. By placing 'a centrally located threaded bore 138 in a raised integral stud 140 on the cap-plate $4, a single hold-down screw 142 may be used to secure the cover portion 136 in position.

The casing 26 may be vented as shown at 144 in FIG- I URE 3 to provide a means for coupling a conduit .to the terminals 122, 126 and 131! of the switch 10.

Operation Referring first to FIGURE 2, as the input or signal pressure in the expansible diaphragm chamber 28, as trans mitted thereto via the inlet port 30 from the pressure inlet range spring 96, causes the transmitting link 36 to force the actuating lever 52 into engagement with the dependent integral limit-stop means 72 on the differential lever 54.

Also referring now to FIGURE 4, the initial counterclockwise rotation of the actuating lever 52, as caused by the above-defined minimum signal pressure, causes a downward movement of the switch engaging detent 62 I011 the said actuating lever which permits a corresponding downward flexing of the contact spring 132 of the switch unit 11 via the push-link 134. The spring 132 is biased to cause the common contact 128 to make with the normally open contact 120 and break with the normally closed contact 124. Thus, the initial movement of the actuating lever '52 in response to the said minimum signalpressure prepares the switch 14) to trip from one position to the other.

Once the actuating lever 52 has engaged the dependent limit stop 72 on the differential lever 54, the force opposing the counter-clockwise rotation of the said levers 52 and 5 about the pivot pin 56 is increased from the minimum force exerted by the range spring to a total force exerted by'the concerted action of the range spring 96 acting on the actuating lever 52 and the differential spring 98 acting on the differential lever 54 at the hollow stud 76 thereof. Thus, in order to trip the switch It), the signal pressure must increase in a differential amount sufficient to overcome the force differential provided by the differential spring 98 and lever 54. a

As soon as the signal pressure has increased sulficiently to overcome the above-defined differential force, the transmitting link 36 from the diaphragm 26 causes the actuating lever 52 and the differential lever 54, via the dependent limit stop 72, to rotate further about the pivot pin 55, causing the switch engaging detent 62 to move downward an amount sufficient to allow the push-link 134 and contact spring 132 to causethe common contact 128 to break with the normally closed contact 124 and make with the normally open contact 126.

Having now been tripped in one direction, the switch 10 is now responsive'tothe opposite sequence of pressure changes as the signal pressure acting on the diaphragm 28 decreases.

An initial decrease in signal pressure in an amount equal to the above-defined differential pressure permits the range and'differential springs 96 and 98, respectively, to force the actuating and differential levers 52 and 54 clockwise about the pivot pin 56 to a point wherein the hollow stud portion 76 of the differential lever 54 engages the stop screw 78 on the insulating base 18. This action removes the force of the differential spring 98 from the system at this point. a 7

Now, as soon as the signal pressure has decreased to a point whereinthe downward force of the range spring W on the hollow stud 64- of the actuating lever 52 is greater than the upward force exerted thereon by the 1 transmitting link 36 from the diaphragm 26, the switch 19 is caused to trip in the other direction. 7

The above-defined minimum signal pressure is selected by turning the adjusting screw 108 on the range springt e to cause the threaded end plate to translate along the said screw 108 and thereby selectively vary the force exerted by the said range spring on the'actuatinglever 52.

In a like manner, the additional differential pressure I needed to trip the switch 10 is selected by theadjustment provided by the corresponding-adjusting screw 11% and end plate 162 acting to selectively vary the 'force exerted by said differential spring on the .ditrerential lever 54.

As can be seen from the foregoing specification and drawings, this invention provides a novel pressure actuated electric switch having a novel and readily adjustable differential lever system therein.

It is to be understood that the embodiment shown and described herein is for the purpose of example only and is not intended to limit the scope of the appended claims.

What is claimed is:

1. A pressure operated electric switch comprising switch means having first and second contact positions, said switch means comprising a pair of fixed contacts, a common contact normally closed with one of said fixed contacts and normally open with respect to the other of said fixed contacts, an elongated contact spring having a fixed end and a free end, said common contact being mounted on the said free end, said contact spring being biased to cause said common contact to make with said other of said fixed contacts and having an integral actuating link extending therefrom; displaceable means adapted to be connected with a source of control pressure and being proportionally responsive to said control pressure; and differential means, interengaging said displaceable means and said actuating link, actuating said switch means at a predetermined control pressure to cause said common contact to break with said one contact and subsequently cause said common contact to make with the other of said fixed contacts upon the occurrence of a predetermined pressure difierential from a preselected control pressure, said differential means comprising, fixed pivot means, an actuating lever pivoted intermediate its ends to said pivot means engaging said displaceable means at one of its ends and said actuating link at its other end, first biasing means constraining said actuating lever to break said common contact with said one contact at said predetermined control pressure, and a differential lever pivoted at one of its ends on said pivot means coextensive with said actuating lever and having its other end free to move, and second biasing means constraining said differential lever to impose a differential constraining force on said actuating lever in the same direction as said first biasing means throughout the range of said pressure differential,

2. The invention defined in claim 1, wherein said displaceable means comprises a flexible diaphragm displaceable by said control pressure and having an integral transmitting link extending therefrom into engagement with said first lever means.

3. The invention defined in claim 1, wherein said diff'erential lever further includes integral stop means adapted to engage said actuating lever when the magnitude of said control pressure is in the differential pressure range between said first and second preselected values whereby relative movement between said first and second lever means is prevented over the said differential pressure range.

4. The invention defined in claim 1, wherein said switch means further includes a first fixed reference, a second fixed reference; wherein said first and second biasing means comprise, respectively, first and second adjustable spring means extending between said fixed references and said actuating and differential levers, respectively; and wherein said second lever means further includes integral stop means adapted to engage said first lever means When the magnitude of said control pressure is in the differential pressure range between said first and second preselected values, thereby preventing relative movement between said first and second lever means over said differential pressure range and providing coaction between said first and second biasing means.

5. In a pressure actuated electric switch including a pressure responsive displaceable means, a differential lever means for providing a two stage actuation of said switch in response to first and second selected values of control pressure comprising first and second lever means, a fixed base, a common pivot means on said base, said first lever means being pivoted intermediate its ends on said pivot means, one end of said first lever means being engaged with said displaceable means and the other end thereof being adapted to actuate said switch, said second lever means being pivoted at one end on said pivot means and having its other end free to move relative to the said one end of said first lever means, first biasing means for said first lever means extending between said one end of said first lever means and a first fixed reference, second biasing means extending between said other end of said second lever means and a second fixed reference, said first biasing means determining said first selected value of control pressure and said second biasing means, in the same direction coacting with said first biasing means, determining said second selected value of said control pressure, and integral stop means on said second lever means adapted to engage said first lever means when the magnitude of said control pressure is Within the differential pressure range between said first and second values, thereby preventing relative movement between said first and second lever means over said differential pressure range and providing coaction between said first and second biasing means.

6. The invention defined in claim 5, wherein said first and second biasing means comprise compression springs of individually preselected strength.

7. The invention defined in claim 5, wherein said first and second biasing means comprise compression springs of individually preselected strength, and wherein said first and second fixed references for said first and second biasing means, respectively, comprise selectively positioned mounting means for varying the bias exerted by said compression springs on said first and second lever means, whereby said first and second values of control pressure may be selectively adjusted.

References Cited by the Examiner UNITED STATES PATENTS 2,389,436 11/45 Kearney 200l53 2,447,894 8/48 Bauman 200-83 2,480,538 8/49 Barr 200-83 BERNARD A. GILHEANY, Primary Examiner. 

1. A PRESSURE OPERATED ELECTRIC SWITCH COMPRISING SWITCH MEANS HAVING FIRST AND SECOND CONTACT POSITIONS, SAID SWITCH MEANS COMPRISING A PAIR OF FIXED CONTACTS, A COMMON CONTACT NORMALLY CLOSED WITH ONE OF SAID FIXED CONTACTS AND NORMALLY OPEN WITH RESPECT TO THE OTHER OF SAID FIXED CONTACTS, AN ELONGATED CONTACT SPRING HAVING A FIXED END AND A FREE END, SAID CONTACT SPRING BEING BIASED TO ON THE SAID FREE END, SAID CONTACT SPRING BEING BIASED TO CAUSE SAID COMMON CONTACT TO MAKE WITH SAID OTHER OF SAID FIXED CONTACTS AND HAVING AN INTEGRAL ACTUATING LINK EXTENDING THEREFROM; DISPLACEABLE MEANS ADAPTED TO BE CONNECTED WITH A SOURCE OF CONTROL PRESSURE AND BEING PROPORTIONALLY RESPONSIVE TO SAID CONTROL PRESSURE; AND DIFFERENTIAL MEANS, INTERENGAGING SAID DISPLACEABLE MEANS AND SAID ACTUATING LINK, ACTUATING SAID SWITCH MEANS AT A PREDETERMINED CONTROL PRESSURE TO CAUSE SAID COMMON CONTACT TO BREAK WITH SAID ONE CONTACT AND SUBSEQUENTLY CAUSE SAID COMMON CONTACT TO MAKE WITH THE OTHER OF SAID FIXED CONTCTS UPON THE OCCURRENCE OF A PREDETERMINED PRESSURE DIFFERENTIAL FROM A PRESELECTED CONTROL PRESSURE, SAID DIFFERENTIAL MEANS COMPRISING, FIXED PIVOT MEANS, AN ACTUATING LEVER PIVOTED INTERMEDIATE ITS ENDS TO SAID PIVOT MEANS ENGAGING SAID DISPLACEABLE MEANS AT ONE OF ITS ENDS AND SAID ACTUATING LINK AT ITS OTHER END, FIRST BIASING MEANS CONSTRAINING SAID ACTUATING LEVER TO BREAK SAID COMMON CONTACT WITH SAID ONE CONTACT AT SAID PREDETERMINED CONTROL PRESSURE, AND A DIFFERENTIAL LEVER PIVOTED AT ONE OF ITS ENDS ON SAID PIVOT MEANS COEXTENSIVE WITH SAID ACTUATING LEVER AND HAVING ITS OTHER END FREE TO MOVE, AND SECOND BIASING MEANS CONSTRAINING SAID DIFFERENTIAL LEVER TO IMPOSE A DIFFERENTIAL CONSTRAINING FORCE ON SAID ACTUATING LEVER IN THE SAME DIRECTION AS SAID FIRST BIASING MEANS THROUGHOUT THE RANGE OF SAID PRESSURE DIFFERENTIAL. 